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in seven days directly from a sputum sample plus the determination of multi-drug resistance. However, the diagnostic test requires an inverted microscope, which is not a cheap piece of equipment and not many laboratories can afford it, especially not Peru’s ministry of health. The MODS reading also requires skilled technicians to interpret the patterns and correctly classify TB. Both of these reasons have meant it’s not been feasible to implement this equipment to any large degree in Peru, although this method is now being used in other countries including Singapore, Thailand, South Africa, Bangladesh, Ecuador and Bolivia. ‘We wanted to find a way of replacing a


costly microscope as well as the skilled technician to make the diagnosis,’ states Dr Zimic. In Peru, most newly-diagnosed patients are automatically put on a 10-month regime of first-line empirical drugs. If the patient doesn’t respond to the treatment, they are declared to have a multi-drug-resistant strain and put on a course of second-line drugs. During this time the patient remains ill and can transmit the disease.


to the problem: firstly, building an inexpensive digital microscope and secondly, developing a mathematical algorithm to automatically identify the Mycobacterium tuberculosis in a digital microscope image. The prototype microscope used optical components from Edmund Optics, including stages, lenses and a 45° mirror to deflect the light beam at 90°. The system was designed to be used for both manual readings


and to capture digital images of the slides, which can be sent for automated analysis at the UPCH-Bioinformatics laboratory servers with the algorithm. The algorithm takes 15 seconds to run on a standard PC and is 99.4 per cent sensitive and 99.7 per cent specific, according to Dr Zimic. ‘We proved that there was no significant


difference between results from our system and a $10,000 Nikon inverted microscope,’ Dr Zimic comments. After the seven-day culture period, the plate can be read under the microscope, the image from which is processed by the automated algorithm at the University servers to make the analysis. ‘The physician will know in seven days, with high accuracy, if the patient has TB


We hope the microscope will reduce diagnosis of drug-resistant TB in Peru from 10 months to seven days


Dr Zimic’s team took a two-pronged approach


and simultaneously if that patient is multi-drug resistant,’ he continues. ‘This test cuts out the 10-month empirical treatment of TB sufferers with first-line drugs by determining multi-drug- resistant strains initially, which means treatment can immediately commence with second-line drugs.’


The microscope can be built for as little as $400-500 using a simple dichroic lamp as the illumination source. Nikon or Olympus inverted microscopes cost from $8,000 upwards. The components from Edmund Optics were used to demonstrate the proof-of-concept system. ‘We bought different sets of lenses and stages from Edmund to design a microscope fit for this


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Dr Mirko Zimic and his team at the Universidad Peruana Cayetano Heredia in Peru have developed a low-cost inverted microscope for diagnosing tuberculosis.


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